The generation of
industrial residues is unavoidable, but these materials may be recovered,
redirecting them toward new production processes, rather than allocating them
to the stream of discards. The aim of this paper is to study the feasibility of
utilization of metallurgical wastes as raw material for tiles in the ceramic
industry, using the residual
materials as aggregates in clay based ceramics. The residues used are: sludge
and slag from several metallurgical processes, Ruthner dust and foundry sand. Samples
were obtained from mixtures of clay and each waste in various percentages,
which were then heat treated. The pieces obtained were characterized using
several techniques, with the aim of determining the properties of these
materials in relation to the commercial requirements. A high feasibility of
reuse of most of these wastes as raw material in the production of ceramic
bodies has been established.
Ba0.5CaxSr0.5-xTiO3 (BCST) ceramics, where x = 0, 0.1, 0.2, 0.3 and 0.4, were prepared by
the conventional solid state reaction technique. X-ray diffraction (XRD)
analysis confirmed the formation of BST perovskite phase structure besides some
calcium oxide peaks for samples with high Ca content, x. Scanning electron
microscopy (SEM) results confirmed the XRD results, i.e., as x increased, the average grain size decreased. Energy
dispersive X-ray (EDX) analysis verified the increase of the amount of Ca
element with increasing of its content. Mechanical properties such as ultrasonic
attenuation, longitudinal wave velocity, and longitudinal elastic modulus were
studied by an ultrasonic pulse echo technique at 2 MHz frequency.
Investigations of ceramic microstructures and mechanical properties showed
their dependence on composition. Increasing of Ca content resulted in a
decrease in bulk density and ultrasonic attenuation and an increase in
porosity, velocity, and modulus. High temperature ultrasonic studies showed, in
addition to Curie phase transition, three or more relaxation peaks and its
origin was investigated.
In this paper we report, for the first time, a new approach for synthesis of high quality faceted microcrystalline coatings of molybdenum (Mo), tungsten (W), their carbides and composites. These studies are carried out using Hot Filament Chemical Vapor Deposition (HF-CVD) method wherein parent materials (Mo and/or W) are taken in the form of wires (~0.5 mmdia) and are heated to a high temperature (TF ~ 1500 - 2000 C), in ambient of “oxygen (O2) diluted hydrogen (H2) gas”. Due to high filament temperature (TF), a series of pyrolytic reactions take place. Firstly, the gasification of wire material (Mo and/or W) occurs in the form of its oxide. The oxide molecules reach the substrate which is kept underneath the filament assembly. Secondly, molecular hydrogen gets dissociated into atomic hydrogen and subsequently reaches the substrate to react with oxide molecules, finally leading to the precipitation of a pure metal. This method can also be used, in situ, to convert metallic coatings into their carbides and/or composites. The method offers many other attractive features, which can not be rendered by the conventionalCVD/PVDmethods. The results are discussed in terms of temperature induced “Red-ox” reactions.